The present invention in the first place is concerned with a contacter or bonder by means of which a thin aluminum wire is welded under the action of pressure and ultrasound to a contact point of electrical or electronic structural elements, particularly semiconductor elements etc. The aluminum wire is applied by a bonding head which comprises a wire supply means and an ultrasonically excitable press die, the so-called wedge.
The structural elements to be bonded are being fed from a magazine to the bonding head by a fixed-cycle conveyor. At the bonding head they are positioned by a retainer or holding means, then they are bonded, and subsequently transported to another magazine. In the bonding, especially of elongated structural elements or structural elements tending to warp and having a plurality of contact surfaces to be bonded, in other words structural element carriers or so-called lead frames, problems are encountered in the accurate positioning or coordination of the same with respect to the bonding head. For instance, contamination of the underside of the frame and/or of the support surface or base of the frame and/or surface irregularities and/or punching inaccuracies (burrs) of the frames will cause the frames not to lie flat or entirely flush on the support or base, when being fixed thereto by a clamp or the like. This will result in an undefined vibrational mode of the frame which may have such an influence on the ultrasonic vibration of the wedge and thereby change the welding process in such a way that the welding or bonding achieved is incomplete. Contaminations etc. of no more than 1 to 2 micrometers may be sufficient to cause that. The production of waste caused by the deficiency described above is correspondingly high.